THE INFLUENCE OF ANULOTOMY SELECTION ON DISC COMPETENCE - A RADIOGRAPHIC, BIOMECHANICAL, AND HISTOLOGIC ANALYSIS

Study Design. This study analyzed the radiographic, biomechanical, and histologic attributes of three commonly used anulotomy techniques. Ob jectives. This study defined the propensity of the anulus fibrosus to heal after discectomy and correlated biomechanical differences between subgroups of the motion segments studied. Summary of Background Data. No previous report that compares the influence of anulotomy selection on disc competence exists. Methods. Anulotomies were performed on the anterolateral aspects of the lumbar discs of 54 adult goats. The goat s were randomly assigned to one of three subgroups containing 18 anima ls. In subgroup A, a full-thickness anular window was excised. In subg roup B, a full-thickness cruciate anulotomy was accomplished. In subgr oup C, a full-thickness anulotomy was developed by inserting a trocar, 2.5 mm in diameter, into the disc. Results. Histologic analysis revea led that primary anular healing did not occur in any specimen. The anu lotomy tracts in subgroup C (trocar) were consistently narrower than t hose of subgroups A and B. Discography demonstrated the presence of se vere and early disc degeneration with subgroup A (anular window), a fi nding not observed within the trocar anulotomy group. Biomechanical te sting demonstrated increased resistance to pull out by the trocar anul otomy group at 4 weeks, as well as increased torsional stiffness of th e motion segment when compared to both window and cruciate anulotomy. Conclusions. The authors conclude that attempts should be made to mini mize injury to the anulus fibrosus during the performance of discectom y.